240 REACTION OF THE INTERIOR OF THE EARTH 



a fissure in the westernmost Cordillera nearest to the 

 Pacific Ocean, without the direction of the axis being 

 coincident with that of the Cordillera. The lofty 

 wall is surmounted, castle-like, by three successive 

 summits from south-west to north-east, called Cuntur- 

 guachana, Gruagua-Pichincha (or the child of the old 

 volcano) and el Picacho de los Ladrillos. The proper 

 volcano is termed " the Father," or " Old Man," " Eucu- 

 Pichincha." It is the only part which enters the 

 region of perpetual snow, rising to a height which ex- 

 ceeds that of Gruagua-Pichincha (the child), by about 

 190 or 200 feet. Three tower-like rocks surround 

 the oval crater, which lies a little to the south-west, 

 therefore, out of the immediate axis, of a rocky wall, of 

 which the mean height is 15,673 feet. In the spring of 

 1802 I reached the summit of the eastern tower in 

 company with the Indian Felipe Aldas. We stood 

 alone there, on the outermost margin of the crater, 

 about 2450 feet high above the floor of the fiery abyss. 

 Sebastian Wisse, to whom the physical sciences owe so 

 many interesting observations made during his long 

 residence in Quito, had the boldness, in 1845, to pass 

 several nights in a part of the crater of Eucu-Pichincha, 

 where, towards sunrise, the thermometer fell 3*6 below 

 the freezing point, or to 28'4. The crater is divided 

 into two parts by a ridge of rock covered with vitrified 

 scoriae. The eastern part is more than a thousand feet 

 lower than the western one and is now the especial seat 

 of volcanic activity. There, a cone of eruption rises to 

 a height of nearly 270 feet, and is surrounded by more 

 than seventy burning fumaroles exhaling sulphureous 

 vapours. ( 333 ) It was probably from this eastern circular 



